900W H-class PA Amp with Limiter

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wg_ski

Member
Joined 2007
I don't know about a MOSFET output stage, but I tried with a quasi-comp bipolar stage and the oscillations were incredible. Every time the negative rail switched it broke into oscillation and went into overcurrent. The same exact circuit with complementary was rock stable. The quasi-comp circuit without the rail switches was also rock-stable. The combination of the two just didn't work.
 
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wg_ski

Member
Joined 2007
andrewlebon said:
hi wg ski
greetings can you please give me some tips to make commutation noise
inaudible as i have had a tough time getting all parts for this project making h class
for the first time so every tip is valuable learning process one has to learn some time
I am just a hobbiyst make for fun any schematic would help waiting for your inputs
apex audio has been a great help thanks to both of you given me the courage to move
on
thanking you
andrew lebon
Click to expand...

The 47 pF caps on each rail switch keep the slew rate under control. It increases the switching time - but not enough to make it ineffective at audio frequency. Switching losses will be noticeable at 20k, but are you going to put that much into your compression drivers? It helps reduce the commutation noise, as do the .1uF/2.2 ohm snubbers. The other thing that slew limiting does is reduce di/dt - to the point where TO-247 package and typical PCB inductances are practical. Too much inductance combined with too fast switching and you get spikes across the PCB traces that last only a few hundred nanoseconds but are deadly. These commutators are the variation of the QSC switch that I use on some of mine. Uses the 311 - so they're an option in places where the IR drivers are difficult to find. The basic amp schematic that I use is similar to Apex's (with the opamp in the input stage and EF outputs).
 

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andrewlebon

andrewlebon

R.I.P.
Joined 2008
hi apex audio
greetings board completed with all parts except nsl 32 used
commutator diode 16 A 600 volts ultra fast can a 35 0 35 and 60 0 60 ac
2 transformers be used for testing for high voltage 10000 uf 100 volt condensers
and for low voltage 10000n uf 63 voltage only for testing only want to test
at low volume is it possible
1 instead of nsl 32 have A 817 optocoupler can it work
thanking you
andrew lebon
 
apexaudio

apexaudio

Member
Joined 2010
andrewlebon said:
hi apex audio
greetings board completed with all parts except nsl 32 used
commutator diode 16 A 600 volts ultra fast can a 35 0 35 and 60 0 60 ac
2 transformers be used for testing for high voltage 10000 uf 100 volt condensers
and for low voltage 10000n uf 63 voltage only for testing only want to test
at low volume is it possible
1 instead of nsl 32 have A 817 optocoupler can it work
thanking you
andrew lebon
Click to expand...
Amp will work without NSL32, just not have limiter. U can put LED diode on place of LDR diode and it will be peak indicator. A817 is optotransistor, and NSL32 is optoresistor, can not work.
Transformers and condensers can be use.
 
apexaudio

apexaudio

Member
Joined 2010
electra_ina said:
Thanks Apex...you are the best my friends...he.he.....I hope, I can build this amplifier and if I found trouble, I will to "see" you againt...Sorry my english..;)
Regards
Electra_ina
Click to expand...
Ok, but do not expect to much help of me, I give U my project as idea for your own project not to teach U about electronic. I give U sufficient information already.
Regards
 
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